The present invention relates to a container having a liquid detecting function (more particularly, an ink residual quantity detecting function) adapted for a liquid ejection device (or a liquid consumption device) such as an inkjet recording device.
As a representative example of a conventional liquid ejection device, there is an inkjet recording device including an inkjet recording head for recording an image. As the other liquid ejection devices, there are, for example, a device including a color material ejection head used for manufacturing a color filer, such as a liquid crystal monitor, and a device including an electrode material (conductive paste) ejection head used for forming an electrode, such as an organic electroluminescence display or a field emission display (FED), a device including a living organic material ejection head used for manufacturing a bio chip, and a device including a sample ejection head as a precise pipette.
In the inkjet recording device which is the representative example of the liquid ejection device, a pressure generating means for, pressuring a pressure generating chamber and an inkjet recording head having a nozzle opening for ejecting pressurized ink as an ink droplet are mounted in a carriage, and the ink in an ink container is continuously fed to the recording head through a channel such that printing is continuously performed. The ink container is a detachable cartridge which can be simply replaced by a user when the ink is used up.
Conventionally, as a method of managing ink consumption of the ink cartridge, there are a method of integrating the quantity of ink sucked by the maintenance or the number of ink droplets ejected from the recording head using software to manage the ink consumption by calculation and a method of attaching an electrode for detecting a liquid level to the ink cartridge to manage a point of time when the ink is actually consumed by a predetermined quantity.
However, the method of integrating the quantity of the ink or the number of ejected ink droplets using the software to manage the ink consumption by calculation has the following problems. There may be a head in which ejected ink droplets have weight variations. The weight variations of the ink droplets do not have influence on image quality. However, in consideration of a case where error in the quantity of the consumed ink due to the variation is accumulated, an excess quantity of ink must be filed in the ink cartridge. Accordingly, the ink may remain by the excess.
On the other hand, since the method of managing the point of time when the ink is consumed by the electrode can detect the actual quantity of the ink, the residual quantity of the ink can be managed with high reliability. However, when the detection of the liquid level of the ink depends on the conductivity of the ink, the kind of the ink which can be detected is restricted or a structure for sealing for the electrode becomes complicate. In addition, since noble metal having excellent corrosion resistance and excellent conductivity is used as the material of the electrode, a cost for manufacturing the ink cartridge increases. Furthermore, since two electrodes need be mounted, the number of steps increases and thus the manufacturing cost more increases.
Accordingly, a device which is developed for solving the problems is disclosed in Patent document 1 as a piezoelectric device (here, referred to as sensor unit). The sensor unit monitors the residual quantity of the ink in the ink cartridge using a change in a resonance frequency of a residual oscillation signal due to residual oscillation (free oscillation) of a diaphragm after forcible oscillation, when the ink exist or not in the cavity facing the diaphragm in which a piezoelectric element is laminated.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-146030.
However, when the sensor unit disclosed in Patent Document 1 is used, the ink must enter up to the cavity facing the diaphragm and be prevented from entering into a side in which the piezoelectric element of an electrical element is provided. Accordingly, adjacent members must be properly sealed when they are assembled.
As a sealing structure, there is provided a structure in which the sensor unit is directly bonded to the periphery of an opening of the container or a structure in which the sensor unit is directly bonded to the periphery of an opening of a module and the module is then attached to a container body through an O-ring. However, in these structures, since the sensor unit is in contact with the periphery of the opening, it is difficult to ensure a sealing property when dimensional variation is generated. In addition, when the sensor unit is directly bonded to the periphery of the opening of the container or the periphery of the opening of the module, the sensor unit is apt to be influenced by fluctuation of ink or air bubble in the ink and thus false detection may be caused.
Furthermore, when this kind of the sensor is completed, a plurality of parts must be adequately assembled. However, when an assembling direction is wrong, yield deteriorates.